feat: add cross-compile Makefile and GitHub Actions release workflow

- Makefile with build (single platform), release (4 targets), clean, test, vet
- GitHub Actions workflow triggers on v* tags, cross-compiles, creates release
- Version embedding via -ldflags -X main.version
- SHA256 checksums for all release binaries
- Add dist/ to .gitignore

Resolves: ISS-36

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: chuongld20

.github/workflows/release.yml

@@ -0,0 +1,30 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: write
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - name: Cross-compile
+        run: make release VERSION=${{ github.ref_name }}
+
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          files: dist/*
+          generate_release_notes: true

.gitignore

@@ -30,6 +30,9 @@ vendor/
 .DS_Store
 Thumbs.db
 
+# Build output
+/dist/
+
 # devbox specific
 devbox.yaml
 *.log

Makefile

@@ -0,0 +1,32 @@
+BINARY    := devbox
+MODULE    := github.com/junixlabs/devbox
+BUILD_DIR := dist
+VERSION   ?= $(shell git describe --tags 2>/dev/null || echo "0.1.0-dev")
+LDFLAGS   := -s -w -X main.version=$(VERSION)
+
+PLATFORMS := linux/amd64 linux/arm64 darwin/amd64 darwin/arm64
+
+.PHONY: build release clean test vet
+
+build:
+	@mkdir -p $(BUILD_DIR)
+	go build -ldflags '$(LDFLAGS)' -o $(BUILD_DIR)/$(BINARY) ./cmd/devbox/
+
+release:
+	@mkdir -p $(BUILD_DIR)
+	@for platform in $(PLATFORMS); do \
+		GOOS=$${platform%/*} GOARCH=$${platform#*/} \
+		go build -ldflags '$(LDFLAGS)' -o $(BUILD_DIR)/$(BINARY)-$${platform%/*}-$${platform#*/} ./cmd/devbox/ && \
+		echo "Built $(BINARY)-$${platform%/*}-$${platform#*/}"; \
+	done
+	@cd $(BUILD_DIR) && sha256sum $(BINARY)-* > checksums.txt
+	@echo "Checksums written to $(BUILD_DIR)/checksums.txt"
+
+clean:
+	rm -rf $(BUILD_DIR)
+
+test:
+	go test ./...
+
+vet:
+	go vet ./...